WO1999023128A1

WO1999023128A1 - Catalyst and method for trimerization of isocyanates

Info

Publication number: WO1999023128A1
Application number: PCT/FR1998/002359
Authority: WO
Inventors: Denis Revelant; Jean-Marie Bernard
Original assignee: Rhodia Chimie
Priority date: 1997-11-04
Filing date: 1998-11-04
Publication date: 1999-05-14
Also published as: BR9813932A; DE69818857D1; KR20010031693A; EP1027380B1; KR100549652B1; ATE251648T1; US20050080259A1; JP4342723B2; DE69818857T2; US7091341B2; US6635761B1; ZA9810038B; JP2001521952A; CN1184248C; AU1159699A; EP1375545B1; EP1375545A1; CN1280588A; CA2307747A1; EP1027380A1

Abstract

The invention concerns the use as cyclotrimerization reaction catalyst of isocyanates of a cation hydrogen carbonate which, either as such, or in complexed form with a complexing agent, has an ionic or molecular radius greater than 1 Å, preferably than 1.5 Å and which is at least partially soluble in the reaction medium. The invention also concerns a method for preparing polyisocyanates (poly)isocyanurates by catalytic cyclotrimerization of isocyanates which consists in using a catalytic system comprising as catalyst a cyclotrimerization catalyst based on quaternary ammonium salt with imidazole as co-catalyst.

Description

CATALYST AND METHOD FOR TRIMERIZATION OF ISOCYANATES

The subject of the invention is a catalyst useful for the catalytic cyclotrimerization of monomeric isocyanates to polyisocyanates.

(poly) isocyanurates, as well as a process for the preparation of polyisocyanates

(poly) isocyanurates by catalytic cyclotrimerization of monomeric isocyanates.

It is known to prepare isocyanate trimers by catalytic trimerization of an isocyanate using a catalyst based on a quaternary ammonium hydroxide.

Thus, EP-003 765 describes the partial cyclotrimerization of isophorone diisocyanate (IPDI or 1 -isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane) using as a catalyst a hydroxide of a hydroxyalkylammonium quaternary.

In general, catalysts based on a quaternary ammonium hydroxide have a very strong reactivity which makes it difficult to control the trimerization reaction, in particular when the starting isocyanate is an aliphatic or cycloaliphatic isocyanate.

In addition, control of the reaction is made even more difficult due to the possible variations in the content of hydrolyzable chlorine in the starting isocyanate, originating from the phosgenation process used for the synthesis of these isocyanates.

It is thus known that the efficiency of the catalyst decreases when the content of hydrolyzable chlorine contained in the IPDI increases.

The hydrolysable chlorine content also influences the coloration of the reaction crude which increases as the quantity of chlorine is high.

US 4,040,992 further describes catalysts for the catalytic trimerization of isocyanates of the quaternary ammonium salt type, the anion of which is represented by OH ^" , or the formula OOC- (O) _a -Y in which Y is chosen from: an atom hydrogen, an alkyl group having from 1 to 20 carbon atoms, an alkenyl group having from 2 to 15 carbon atoms, a cycloalkyl group having from 3 to 6 carbon atoms, a phenyl group, an alkylphenyl group having from 1 to 9 carbon atoms in the alkyl radical or in the groups linked to the phenyl ring, a benzyl group, a carbamate group, a group alkylbenzyl having from 1 to 9 carbon atoms in the alkyl residue or in the groups linked to the benzyl ring, and a group CH _(3. _b) Z ( _b ) in which b is an integer from 1 to 3 and Z is OH , CN, Cl, an aikoxy group of 1 to 5 carbon atoms, or a phenyl or methoxyphenyl group, or

Z is (CH ₂ ) _d COOR in which d is an integer from 0 to 4 and R is a hydrogen atom or an alkyl group having up to 20 carbon atoms, and a is zero or 1

However, the anions illustrated in this patent are all anions derived from alkylcarboxylic acid. In general, the catalysts described in this document do not make it possible to achieve the desired goal.

The object of the invention is to provide a catalyst for cyclotrimerization of isocyanates, in particular dnsocyanates which allows control of the reaction, while having an acceptable conversion rate, which is not substantially dependent on the chlorine content. hydrolyzable, starting isocyanate and making it possible to obtain a product whose coloring is not marked markedly. The aim of the invention is also to propose a process for the catalytic trimerization of isocyanates, in particular for cyclotimerization partial dnsocyanates, which is easy to control, does not depend or little depends on the content of hydrolyzable chlorine present in the isocyanate monomer and which reduces as much as possible the coloration of the reaction crude

We have now surprisingly discovered that ionic type catalysts, the counter anion of which is the hydrogen carbonate anion, would make it possible to achieve the desired goal. These catalysts are formed from a bulky mono-atomic or poly-atomic cation, either as such or in the form of a complex formed with a complexing agent, in particular of the encryption type.

A subject of the invention is thus the use as a catalyst for the cyclotrimerization reaction of isocyanates of a hydrogen carbonate of a cation which, either as such, or in form complexed with a complexing agent, has an ionic radius or average molecular greater than 1 Â, preferably greater than 1.5 Â, as defined in the tables of M. Shannon and Prewitt in Acta Cris, 1969, vol. B25, page 925 and which is at least partially soluble in the reaction medium.

Advantageously, the cation is chosen from cations of bulky alkali metals, in particular rubidium and cesium.

The cation can also consist of a cation of light alkali metal, in complexed form. Mention may in particular be made of the sodium and potassium cations complexed with crown ether.

The cation can also consist of a molecular species, in which all the atoms are linked by covalent bonds.

In this respect, mention will be made of "onium" type cations, the representative species of which are phosphoniums, sulfoniums and quaternary ammoniums.

Particularly preferred are the hydrogen carbonates of the cations of formula I below:

in which

Q represents a nitrogen, phosphorus or sulfur atom; and Ri, R ₂ , R _{3 and} R _4, identical or different, denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having from 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, radicals aralkyl having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups or when Q is N, two of the residues Ri, R ₂ , R ₃ or R ₄ may also form, with the nitrogen atom and, where appropriate, with a hetero atom, in particular of oxygen or nitrogen, a heterocyclic ring having 4 to 6 carbon atoms, or else when Q is N , the residues Ri, R ₂ and R ₃ each represent ethylene residues which form, in association with the quaternary nitrogen atom and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton, or one of R to R ₄ represents a group

R7

in which R ₅ , Re and R _{7, which are} identical or different, represent hydrogen, an OH group, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having from 2 to 15 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 atoms of carbon or a group R ₈ -0- (CH ₂ ) _n in which R ₈ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, a residue aralkyl having 7 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms; and n is an integer ranging from 1 to 6; R ₇ can also also represent an OCOR ₉ group, R9 being a Cι-C ₆ alkyl group, preferably dC ₄ , more particularly the methyl group. The cation is more particularly represented by the following general formula II:

Ri, R ₂ and R ₃ represent identical or different radicals and denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, aralkyl radicals having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups, two of the residues Ri, R ₂ or R ₃ can also form with l nitrogen and, where appropriate, with an oxygen hetero atom or another nitrogen hetero atom a heterocyclic ring having 4 to 6 carbon atoms, or else the residues R _{1 (} R ₂ and R ₃ representing each of the ethylene residues which form, in association with the quaternary nitrogen atom and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton,

R ₅ , R ₆ and R _{7, which are} identical or different, represent hydrogen, an OH group, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having from 2 to 15 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms carbon or a group R ₈ -0- (CH ₂ ) _n in which R ₈ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, an aralkyl residue having from 7 to 10 carbon atoms or an aryl residue having from 6 to 10 carbon atoms; and n is an integer ranging from 1 to 6; R ₇ can also represent a group OCORg, R ₉ being a Cι-C ₆ alkyl group, preferably Cι-C ₄ alkyl, more particularly the methyl group.

A group of preferred quaternary ammonium cations consists of the compounds in which: - Ri, R ₂ and R ₃ identical or different represent a linear Cι-C ₄ alkyl group, preferably C1-C3 alkyl, more particularly alkyl in Cι-C ₂ , and preferably methyl,

- R ₅ represents H, OH, the methyl group or the hydroxymethyl group, - R ₆ represents H, OH, the methyl group or the hydroxymethyl group,

R ₇ represents H, OH, the methyl group, the hydroxymethyl group or the acetyl group,

Another group of preferred quaternary ammonium cations consists of the compounds in which:

- Ri, R ₂ and R ₃ identical or different represent a Cι-C ₄ alkyl group, preferably C ₁ -C ₃ alkyl, more particularly C -C ₂ alkyl, and preferably methyl,

- R ₅ represents H or a Cι-C ₄ alkyl group, - R ₆ represents H, OH or a Cι-C ₄ alkyl group,

- R ₇ represents H, OH, alkyl dC ₄ or acetyl. without the total of the carbon atoms from ^ to R ₇ exceeding 8, preferably 6. More advantageously still, the quaternary ammonium cations are preferred in which at least one, preferably two and more preferably the three groups of R _η to R ₃ represent the methyl group, R ₅ , R ₆ and R ₇ being as defined above, and preferably only one of R ₅ to R ₇ being OH.

Another group of preferred quaternary ammonium cations is that wherein R to R ₃ are alkyl, Cι-C _4, a hydroxyalkyl group Cι-C _4, and R ₅ to R ₇ represent H or OH, said compounds advantageously comprising a single OH group in an omega position relative to the central nitrogen atom.

A more particularly preferred catalyst is choline hydrogenocarbonate, in particular when the isocyanate which it is desired to cyclotimerize is a cycloaliphatic diisocyanate, such as NBDI, IPDI or Hι ₂ MDI, or a mixture of a cycloaliphatic diisocyanate as previously mentioned and of a straight chain or branched chain aliphatic diisocyanate, in particular HDI.

Mention may also be made of tetramethyl phosphonium or sulfonium hydrogen carbonate as well as tetraphenyl phosphonium or sulfonium hydrogen carbonate.

The catalysts according to the invention are known compounds. They can be obtained in particular in the case of quaternary ammoniums, when R represents OH by reaction of a tertiary amine of general formula II:

R ₂ - N ₃ ^κ <»>

in which Ri to R ₃ are as defined above with an epoxide of general formula III:

in which R ₄ and R ₅ are as defined above, in the presence of C0 ₂ and H ₂ 0. In the case of esters, the hydroxylated quaternary ammonium can be esterified using an acylimidazole by example. In the case of ethers, we will work with an excess of epoxy. The catalyst according to the invention can be used for the cyclotrimerization of any type of isocyanates, or mixture of isocyanates whether they are aliphatic, cycloaliphatic or aromatic, including the prepolymers having terminal isocyanate groups, in particular those described in US 5,115,071 the content of which is incorporated by reference in the present application. It can thus be used for the trimerization of isocyanates in the presence of various diols, triols and other polyols whose molecular weights are in a wide range, including polyols and aminopolyols comprising polyether and polyester groups, used for the production of polyurethane resins and polyisocyanurates.

It is advantageously used for the cyclotrimerization of IPDI (isophorone diisocyanate or 1-isocyanato-3,3,5-trimethyl-5-isocyanato methyl cyclohexane), NBDI (norbomane diisocyanate or 2,5 (6) -diisocyanato-methyl -bicyclo [2,2,1] heptane) and Hι ₂ MDI (4,4'-diisocyanate- dicyclohexylmethanediyl), alone or as a mixture with other diisocyanates, in particular with a linear aliphatic chain, such as HDI (hexamethylene diisocyanate).

Advantageously, the catalyst according to the invention is added in an amount between 300 and 5000 ppm, preferably between 500 and 3500 ppm relative to the total amount of the starting isocyanates.

The catalyst is added to the reaction medium with stirring, preferably in the absence of solvent. The reaction is allowed to proceed for a period varying between 1 h and 4 h, preferably approximately one and a half hours.

The reaction is advantageously carried out at a temperature between room temperature and 120 ° C, preferably between 40 and

100 ° C, advantageously under a neutral atmosphere.

The invention also relates to the use of the catalyst in a solid form such as for example obtained by deposition of the catalyst on a mineral such as silica, or by covalent fixing on a resin.

The invention also relates to a process for catalytic trimerization of isocyanates, in particular diisocyanates or of a mixture isocyanates, in particular diisocyanates, characterized in that a quaternary ammonium hydrogenocarbonate as defined above is used as the trimerization catalyst.

It has further been discovered that the cyclotrimerization reaction can be improved substantially when using imidazole or one of its derivatives as a co-catalyst of a catalytic system based on a quaternary ammonium salt.

The invention therefore also relates to a process for the preparation of isocyanurate polyisocyanates by catalytic cyclotrimerization of isocyanates in which a catalytic system is used comprising as catalyst a cyclotrimerization catalyst based on a quaternary ammonium salt and as co -catalyst imidazole or one of its derivatives.

The term “imidazole derivatives” means any compound comprising the imidazole ring and carrying one or more substituents customary in organic chemistry.

The imidazole derivatives correspond in particular to the general formula I:

(R ₃ ) n

in which R ,, R ₂ and R _{3, which are} identical or different, are chosen from H, OH, SH, a C 1 -C alkyl group, C ₁ -C ₄ hydroxyalkyl, C ₁ -C ₄ aminoalkyl, C ₁ -C C alkylamino, dialkylamino ( each alkyl group having from 1 to 4 carbon atoms), Cι-C ₄ alkylthio, C1-C4 haloalkyl, C ₃ -Cs cycloalkyl, C ₅ -Cι ₀ aryl, (C ₅ -C ₁₀ aryl) ; - d-C alkyl; (dC alkyl), - C5-C10 aryl, heterocyclic in which the heterocycle comprises from 2 to 10 carbon atoms and from 1 to 4 identical heteroatoms or different chosen from 0, S and N and the group NR, R ₄ being in particular Cι-C alkyl or C ₃ -C ₈ cycloalkyl and n is equal to 0.1 or 2.

Advantageously, the catalyst based on a quaternary ammonium salt is as defined above.

However, any type of known cyclotrimerization catalyst of the quaternary ammonium salt type can be used.

Mention may in particular be made of the salts of the compounds of the following general formula:

in which

Ri, R ₂ and R ₃ represent identical or different radicals and denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, aralkyl radicals having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups, two of the radicals R ^ R ₂ or R ₃ can also form with l nitrogen and, where appropriate, with an oxygen hetero atom or another nitrogen hetero atom a heterocyclic ring having 4 to 6 carbon atoms, or else the residues R ^ R ₂ and R ₃ representing each of the ethylene residues which form, in association with the quaternary nitrogen atom and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton,

R and R _{5, which are} identical or different, represent hydrogen and / or an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having 2 to 15 carbon atoms an alkynyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or a group R ₆ -0- (CH ₂ ) _n in which R ₆ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, an aralkyl residue having from 7 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms; and n is an integer having a value from 1 to 6; and

X ^" represents an anion, advantageously chosen from OH ^" , and the anions of formula ^' OOC- (O) _a -Y in which Y is chosen from a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an alkenyl group having from 2 to 15 carbon atoms, a cycloalkyl group having from 3 to 6 carbon atoms, a phenyl group, an alkylphenyl group having from 1 to 9 carbon atoms in the alkyl residue or in the groups linked to the nucleus phenyl, a benzyl group, a carbamate group, an alkylbenzyl group having from 1 to 9 carbon atoms in the alkyl radical or in the groups linked to the benzyl ring, and a CH _(3-b ) Z ₍ b) group in which b is an integer of 1 to 3 and Z is OH, CN, Cl, an aikoxy group of 1 to 5 carbon atoms, or a phenyl or methoxyphenyl group, or Z is (CH ₂ ) _d COOR in which d is a number integer from 0 to 4 and

R is a hydrogen atom or an alkyl group having up to 20 carbon atoms; and a is equal to zero or 1. X preferably represents the carboxylate anions and the HCO ₃ ^" anion. The compounds of general formula above are described in

EP 3765 and US 4,040,992, the content of which is incorporated by reference in the present application. When the isocyanate which it is desired to cyclotimerize is a cycloaliphatic diisocyanate, such as NBDI, IPDI or H ₁₂ MDI, or a mixture of a cycloaliphatic diisocyanate and an aliphatic diisocyanate with a straight chain, in particular HDI , it is preferable to use as catalyst a hydrogenocarbonate of a quaternary ammonium, as defined above, in particular choline hydrogen carbonate.

The use of a catalytic system comprising a quaternary ammonium salt and imidazole or derivatives, in accordance with the present invention, makes it possible to achieve an increase in the reactivity of isocyanates, in particular cycloaliphatic isocyanates, the where appropriate, in admixture with straight chain aliphatic isocyanates, which reactivity can be effectively controlled without depending substantially on the hydrolyzable chlorine content of the starting monomeric isocyanate (s) .

In addition, the reaction mixture obtained at the end of the cyclotrimerization reaction, where appropriate, partial, exhibits a strongly attenuated coloring compared to a reaction mixture obtained in the absence of imidazole. Furthermore, the use of imidazole as a co-catalyst of a cyclotrimerization reaction in which the catalyst is a quaternary ammonium salt, results in the formation of a substantial amount of dimers with a uretdione ring of (s ) (l ') isocyanate (s) starting, capable of improving the properties of the resulting mixture, in particular to reduce the viscosity of polyisocyanates isocyanurates.

Advantageously, the imidazole is added with stirring to the isocyanate monomer (s) which it is desired to polymerize, preferably in the absence of solvent, and the stirring is continued until a homogeneous mixture is obtained.

The catalyst is added while stirring is maintained and the reaction medium is heated. The reaction is allowed to proceed for a period varying between 1 h and 4 h, preferably approximately 1 hour and a half.

The use of imidazole as a co-catalyst also makes it possible to substantially reduce the amount of catalyst necessary for the cyclotrimerization of (is) (is) isocyanate (s).

It suffices for example to use an amount of catalyst ranging from 100 to 300 ppm, preferably about 200 ppm, relative to the amount of starting isocyanate (s), when the amount of cocatalyst is 400 to 800 ppm, preferably around 600 ppm, based on the amount of starting isocyanate (s).

The cyclotrimerization reaction, in particular partial cyclotrimerization reaction is carried out at a temperature between room temperature and 120 ° C, advantageously from 60 to 70 ° C for IPDI.

The subject of the invention is also a polyisocyanate (poly) isocyanurate composition obtained by the process according to the invention, in particular comprising the following compounds:

- the NBDI trimer,

- the trimer of Hι ₂ MDI, - the trimer of IPDI,

- the NBDI, IPDI / HDI or H ₁₂ MDI / HDI mixed trimers, in which the proportion of HDI can vary from 5 to 95% by weight.

The subject of the invention is also a composition of polyisocyanates (poly) isocyanurates obtained by the process according to the invention, such a composition being characterized by the presence of reaction products between the starting isocyanate and the imidazole and between the products for the polymerization of these isocyanates, in particular in the form of isocyanurates with imidazole or one of its derivatives, these products possibly also comprising biuret, carbamate and / or allophanate groups obtained by reaction of the isocyanate groups with the OH groups present in the catalyst . The products obtained can subsequently undergo a chemical reaction: dimerization, allophanation, biuretization, blocking reaction with a blocking (or masking) agent either before or after distillation of the monomer.

The compounds obtained are used for the preparation of coatings, in particular as basic constituents for varnishes and paints.

The following examples illustrate the invention.

EXAMPLE 1 Preparation of isophorone diisocyanate trimer (IPDT).

Charged into a reactor is 11.800 g of IPDI. The mixture is stirred under a stream of argon and the temperature is brought to 85 ° C. When the temperature has stabilized, 0.56 g (0.07% by weight) of choline bicarbonate is loaded. The reaction is allowed to continue for 3 hours, following the evolution of the IPDI transformation rate by measuring the titer in NCO (by potentiometry).

80 g of IPDT are obtained, corresponding to a conversion rate of 10%.

EXAMPLE 2 Preparation of isophorone diisocyanate trimer (IPDT). The procedure is as for Example 1 except that 1.6 g are added.

(0.2% by weight) of choline bicarbonate and the reaction is heated to 60 ° C.

320 g of IPDT are obtained, corresponding to an IPDI transformation rate of 40%. EXAMPLES 3 to 5: Comparative examples

The reactivity of choline hydrogen carbonate has also been compared to that of choline hydroxide, choline bisulfite and choline bitartrate.

The results of Examples 1 to 5 are reported in the table below.

^* The [cata] are calculated from 100% choline salts.

It appears that of the different choline salts, only bicarbonate has a weaker and more easily controllable catalytic activity, namely an activity 2.8 times less than that of choline hydroxide.

EXAMPLE 6 Preparation of IPDT

The IPDI (800 g) is loaded into a reactor of 11, and stirred under a stream of argon.

Imidazole is introduced at a rate of 4 mmol / 100 g of IPDI at room temperature. Stirring is maintained and the reaction medium is brought to 80 ° C. When the temperature has stabilized, choline bicarbonate (0.05% by weight) is introduced. The evolution of the reaction is followed by measuring the transformation rate (TT) of the IPDI of time by measuring the titer in NCO (potentiometry). 99/23128

16

The reaction is continued for a period of 1 hour 30 minutes. The conversion rate of the IPDI obtained is of the order of 70%.

EXAMPLE 7: Preparation of IPDT

The procedure is as in Example 6 except that the amount of catalyst introduced is 0.028% by weight.

The reaction is continued at 80 ° C for a period of two hours. The IPDI transformation rate is 60%.

EXAMPLES 8 and 9: Comparative example

The procedure is as in Example 6 except that no imidazole is introduced. The amounts of catalyst (choline hydrogenocarbonate) are 0.2% and 0.15% by weight.

The coloring of the reaction medium is evaluated according to the AFNOR NF T20605 or ASTM 01209.84 method.

In order to promote reactivity and limit the development of coloration, the IPDI is redistilled before the trimerization reaction.

The results are reported in the table below.

The redistribution of the IPDI does not bring any improvement in the coloring of the synthetic crude (140 Apha). On the other hand, the kinetics of transformation is much faster. A 25% drop in the catalyst content (Example 9) limits the degree of conversion of the IPDI but remains without effect with regard to the coloring.

The addition of imidazole, surprisingly, strongly accelerates the kinetics of trimerization, even with a catalyst content eight times lower (example 7) while reducing the coloration of the crude oil by half (60-70 Apha). In addition, the formation of IPDI trimer is accompanied by the co-production of dimer.

The kinetics of trimerization are shown in the appended figure. The effect of imidazole on the initial rate of transformation is spectacular, the reaction times required are halved (slower end of reaction). It is not necessary to deactivate the catalyst, which would suggest in situ decomposition.

Claims

1. Use as a cyclotimerization reaction catalyst of isocyanates of a hydrogenocarbonate of a cation which, either as such, or in complexed form with a complexing agent, has an average ionic or molecular radius greater than 1 Â , preferably 1.5 A, and which is at least partially soluble in the reaction medium.

2. Use according to claim 1, characterized in that the cation corresponds to the general formula I:

in which

Q represents a nitrogen, phosphorus or sulfur atom; and Ri, R ₂ , R ₃ and R _{4, which may be} identical or different, denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, aralkyl radicals having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups or when Q is N, two of the radicals R ^ R ₂ , R ₃ or _R4 can also form, with the nitrogen atom and, where appropriate, with a hetero atom, in particular oxygen or nitrogen, a heterocyclic ring having 4 to 6 carbon atoms, or else when Q is N , the residues R _{1 t} R ₂ and R ₃ each represent ethylene residues which form in association with the quaternary nitrogen atom and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton, or one of Rt to R ₄ represents a group

^R ?

in which R ₅ , R ₆ and R _{7, which are} identical or different, represent hydrogen, an OH group, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having 2 15 carbon atoms, an alkynyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or a group R ₈ -0- (CH ₂ ) _n in which R ₈ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, a aralkyl residue having 7 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms; and n is an integer ranging from 1 to 6; R ₇ can also also represent an OCOR ₉ group, Rg being a Cι-C ₆ , preferably C ₁ -C, alkyl group, more particularly the methyl group.

3. Use according to claim 2, characterized in that the cation corresponds to the following general formula II:

in which

Ri, R ₂ and R ₃ represent identical or different radicals and denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, aralkyl radicals having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups, two of the residues R _{1 (} R ₂ or R ₃ can also form with the nitrogen atom and, where appropriate, with an oxygen hetero atom or another nitrogen hetero atom a heterocyclic ring having 4 to 6 carbon atoms, or else the residues Ri, R ₂ and R ₃ each represent ethylene residues which form, in association with the quaternary nitrogen atom and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton,

R ₅ , Rβ and R _{7, which are} identical or different, represent hydrogen, an OH group, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having 2 to 15 atoms carbon, an alkynyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or a group R ₈ -0- (CH ₂ ) _n in which R ₈ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, an aralkyl residue having from 7 to 10 carbon atoms or an aryl residue having from 6 to 10 carbon atoms; and n is an integer ranging from 1 to 6; R ₇ can also also represent an OCORg group, R ₉ being a CC ₆ alkyl group, preferably Cι-C ₄ , more particularly the methyl group.

4. Use according to claim 1, characterized in that: - R ^, R ₂ and R ₃ identical or different represent a linear Cι-C ₄ alkyl group, preferably dC ₃ alkyl, more particularly Cι-C alkyl ₂ , and preferably methyl, - R ₅ represents H, OH, the methyl group or the hydroxymethyl group,

- R ₆ represents H, OH, the methyl group or the hydroxymethyl group, - R ₇ represents H, OH, the methyl group, the hydroxymethyl group or the acetyl group.

5. Use according to claim 1, characterized in that:

- R ,, R and R ₃ identical or different represent a C ₁ -C ₄ alkyl group, preferably C1-C3 alkyl, more particularly Cι-C ₂ alkyl, and preferably methyl,

- R ₅ represents H or a Cι-C ₄ alkyl group,

- R ₆ represents H, OH or a Cι-C ₄ alkyl group,

- R ₇ represents H, OH, a Cι-C ₄ alkyl group or the acetyl group, without the total of the carbon atoms from R 1 to R ₇ exceeding 8, preferably 6.

6. Use according to claim 1, characterized in that at least one, preferably two and more preferably the three groups from R 1 to R ₃ represent the methyl group, R ₅ , R _Θ and R ₇ being as defined above, and preferably only one of R ₅ to R being OH.

7. Use according to claim 1, characterized in that Ri to R ₃ represent a Cι-C ₄ alkyl group, a hydroxyalkyl group d- C ₄ , and R ₅ to R ₇ represent H or OH, said compounds advantageously comprising a single OH group in an omega position relative to the central nitrogen atom.

8. Use according to claim 1, characterized in that the compound is choline hydrogen carbonate.

9. Use according to any one of the preceding claims, characterized in that the quantity of catalyst is 300 ppm at 5000 ppm, advantageously from 100 ppm to 3500 ppm, relative to the isocyanate monomer or to the mixture of isocyanate monomers.

10. Use according to claim 1, characterized in that the catalyst is in solid form obtained by depositing the hydrogen carbonate on a solid or covaited fixing on a support.

11. Process for the preparation of polyisocyanates (poly) isocyanurates by catalytic cyclotrimerization of isocyanates in which a catalytic system is used comprising as catalyst a cyclotrimerization catalyst based on a quaternary ammonium salt and as co-catalyst the imidazole or one of its derivatives.

12. Method according to claim 11, characterized in that the cyclotrimerization catalyst is as defined in claims 1 to 10.

13. Method according to claim 11, characterized in that the quaternary ammonium salt is of general formula:

in which

Ri, R ₂ and R ₃ represent identical or different radicals and denote alkyl groups, optionally hydroxylated, having 1 to 20 carbon atoms, cycloalkyl radicals having 4 to 15 carbon atoms, optionally substituted with hydroxyl groups, aralkyl radicals having 7 to 15 carbon atoms, optionally substituted with hydroxyl groups or aryl radicals having 6 to 15 carbon atoms, optionally substituted with hydroxyl groups, two of the residues R _1t R ₂ or R ₃ can also form with l nitrogen and, where appropriate, with a hetero atom of oxygen or another hetero-nitrogen atom a heterocyclic ring having 4 to 6 carbon atoms, or else the residues R 1, R ₂ and R ₃ each representing ethylene residues which form in association with the quaternary atom of nitrogen and another tertiary nitrogen atom, a bicyclic triethylenediamine skeleton,

R ₄ and R _{5, which are} identical or different, represent hydrogen and / or an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, a alkenyl group having 3 to 6 carbon atoms, a hydroxyalkyl group having 1 to 9 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or an R group ₆ -0- (CH ₂ ) _n in which R ₆ is hydrogen, an alkyl residue having from 1 to 12 carbon atoms, a cycloalkyl residue having from 4 to 10 carbon atoms, an aralkyl residue having from 7 to 10 carbon atoms or an aryl residue having 6 to 10 carbon atoms; and n is an integer having a value from 1 to 6; and

X ^" represents an anion, advantageously chosen from OH ^" , and the anions of formula ^" OOC- (0) _a -Y in which Y is chosen from a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, an alkenyl group having from 2 to 15 carbon atoms, a cycloalkyl group having from 3 to 6 carbon atoms, a phenyl group, an alkylphenyl group having from 1 to 9 carbon atoms in the alkyl residue or in the groups linked to the nucleus phenyl, a benzyl group, an alkylbenzyl group having from 1 to 9 carbon atoms in the alkyl residue or in the groups linked to the benzyl ring, and a group CH _(3. _b ) Z () in which b is an integer of 1 to 3 and Z is OH, CN, Cl, an aikoxy group of 1 to 5 carbon atoms, or a phenyl or methoxyphéπyle group, or Z is (CH ₂ ) _d COOR in which d is an integer from 0 to 4 and R is a hydrogen atom or an alkyl group having up to 20 carbon atoms,

and a is zero or 1.

14. Method according to claim 11 or 12, characterized in that the quaternary ammonium is choline.

15. Method according to any one of claims 11 to 14, characterized in that the co-catalyst corresponds to the general formula I:

(R ₃ ) n

wherein R ^ R ₂ and R ₃ identical or different are selected from H, OH, SH, alkyl, Cι-C hydroxyalkyl, dC, amino-Cι-C ₄ alkylamino, Cι-C ₄ dialkylamino (each alkyl group having 1 to 4 carbon atoms), Cι-C alkylthio, Cι-C ₄ haloalkyl, C ₃ -C ₈ cycloalkyl, - C5-C10 aryl, (C5-C10 aryl); - Cι-C ₄ alkyl, (CC ₄ alkyl); - C5-C10 aryl, heterocycic in which the heterocycle comprises from 2 to 10 carbon atoms and from 1 to 4 identical or different heteroatoms chosen from 0, S and N and the group NR ₄ , R ₄ being in particular Cι alkyl- C ₄ or C ₃ -C ₈ cycloalkyl and n is 0.1 or 2.

16. Method according to any one of claims 11 to 15, characterized in that the quantity of catalyst is from 100 ppm to 300 ppm, advantageously approximately 200 ppm relative to the monomeric isocyanate.

17. Method according to any one of claims 11 to 16, characterized in that the amount of cocatalyst is from 400 ppm to 800 ppm, advantageously about 600 ppm relative to the isocyanate monomer.

18. Use according to any one of the preceding claims, for the preparation of the trimer of isophorone diisocyanate or of a mixed trimer diisophorone diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% by weight.

19. Method according to any one of the preceding claims, for the preparation of the trimer of isophorone diisocyanate or of a mixed trimer diisophorone diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% by weight

20. Use according to any one of claims 1 to 10, for the preparation of the norbomane diisocyanate trimer or of a mixed trimer of norbomane diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% in weight.

21. Process according to any one of claims 11 to 17, for the preparation of the norbomane diisocyanate trimer or of a mixed trimer of norbomane diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% in weight.

22. Use according to any one of claims 1 to 10, for the preparation of the 4,4'-dicyclohexylmethanediyl diisocyanate trimer or of a mixed trimer of 4,4'-dicyclohexylmethaπediyl diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% by weight.

23. Process according to any one of claims 11 to 17, for the preparation of the 4,4'-dicyclohexylmethanediyl diisocyanate trimer or of a mixed trimer of 4,4'-dicyclohexylmethanediyl diisocyanate and of hexamethylene diisocyanate in which the proportion of hexamethylene diisocyanate varies from 5 to 95% by weight.

24. Composition of polyisocyanates (poly) isocyanurates obtained by the process according to any one of claims 11 to 17, comprising the reaction product of the isocyanate monomer and / or trimer with imidazole or one of its derivatives.

25. Composition of polyisocyanates (poly) isocyanurates obtained by cyclotrimerization of isocyanates alone or as a mixture using a catalyst as defined in claims 1 to 10, or by carrying out a process as defined in l any of claims 11 to 17.